The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Internal combustion engines combust a fuel and air mixture within cylinders driving pistons to produce drive torque. The engine drives a transmission through a coupling device. Coupling devices for automatic transmissions include a torque converter. The transmission transfers the drive torque to a driveline through one of a plurality of gear ratios. The transmission shifts between gear ratios based on a shift schedule and vehicle operating conditions.
The transmission typically includes a plurality of clutches that are selectively engaged to establish a desired gear ratio. When shifting between gear ratios, clutch-to-clutch shifts occur. More specifically, at least one clutch is disengaged (i.e., an off-going clutch) while another clutch is concurrently engaged (i.e., an on-coming clutch). Control of the clutch-to-clutch shift is based on an estimated engine torque and other shift parameters including, but not limited to, an on-coming pressure offset, an off-going pressure offset, and a pressure hysteresis.
After initial assembly of the vehicle and/or after service has been performed on the transmission, the shift parameters are set to initial values and are not influenced by the adaptive/learned shift control. The on-coming pressure offset, the off-going pressure offset, and the pressure hysteresis for each clutch are adaptively learned and updated during vehicle operation. The estimated engine torque is determined using a torque estimating calculation that is based on engine operating conditions.